Silver halide-utilized photographic materials, namely silver salt photographic systems, have undergone accelerative development in recent years; as a result, color images of high quality can be got with ease at the present time. Owing to the highly advanced recent developments in generally used color photographic processes and the spread of not only the so-called color labo, or photofinishing laboratories for highly efficient mass-production of color prints, as large-scale local bases but also the so-called mini-labo, or small-sized simplified print processors installed in stores, everybody can be easily amused with color photographs.
Further, the APS system embodying a new concept has been lately introduced into the market. In such a system, a magnetic substance-applied support is used in color negative films and diverse information can be recorded thereon as magnetic record. That system proposes new ways of enjoying photographs. Therein, for instance, changes in print size can be introduced by facilitating the handling of films and recording the information at the time of photographing. In addition, tools for editing and processing the image information read from processed negative films by means of a simple scanner have been proposed. By utilizing such a method, high-quality image information from silver salt photographs can be readily converted into digital information, and so a wide range of applications going over the conventional ways of enjoying photographs are being popularized.
On the other hand, the so-called digital still cameras using CCD as image pickup elements are making rapid progress in their performance. With respect to the cameras intended for amateur use, it was these several years ago that the cameras loaded with CCD elements having more than several millions of pixels were beginning to appear on the market. Unlike general color photographic systems, the digital still cameras require no processes for developing exposed films, but they can directly provide digitized image information. Therefore, the taken images can be checked at once on a liquid crystal monitor, and the digital information obtained can be easily utilized for various purposes. It is also possible to transfer such image information to a printer, thereby making prints with ease. Further, the image information can be processed variously with a personal computer and enables easy transfer via internet. The latest increase in density of CCD and the recent advance in performance of mass digital data-handling apparatus have come to ensure the image quality worth viewing as photographs for the images printed; as a result, discussion has opened up over the probability of substitution of those digital still cameras for conventional cameras used in photography.
Under these circumstances, it is desired to pursue higher photographic speed and higher latitude at silver halide photosensitive materials from the viewpoint of further development of the silver salt photographic system in opposition to the digital still camera system. Although remarkable improvements have been made in CCD characteristics as the image pickup element of a digital still camera, there is a limit to the photographic speed which can be heightened, increasing the number of pixels in the element of a limited size. Further, it is difficult in principle to ensure high latitude under price and convenience restrictions imposed on the camera system. Therefore, if the silver halide photosensitive materials can achieve higher photographic speed and higher latitude than ever and can be loaded in inexpensively and handy goods, such as lens-attached films, an attractive system can be offered to users.
The photographic speeds of silver halide photosensitive materials have been increased as times have passed, and the color negative films prevalent on the current market have the photographic speed of ISO 400. However, even such a speed is not enough for enjoyment of taking photographs at any time and at any place without auxiliary means such as a strong strobe light. The commercial ultrahigh-speed films having the photographic speed of ISO 1600 or ISO 3200 are on the market today. These films can advance the limits of photography, indeed, but further increase in photographic speed is to be desired. However, with the further increase in photographic speed, the photographic materials using silver halide grains as a photosensitive element come to bear various problems.
For the increase in photographic speed of a silver halide photosensitive material, it is effective to increase the grain size of silver halide grains used in the photosensitive material. In general, however, the use of coarse grains often deteriorates the granularity of the image formed, and thereby the image quality is marred. As an effective means to improve this situation, it is usable to increase the number of silver halide grains present in a unit area of a photosensitive material. In addition, increasing the number of silver halide grains per unit area is also effective for efficiently capturing rays of light incident on the film. Therefore, there is a general tendency for color negative films available at stores to have a greater rise in silver coverage with the increase in their photographic speed. In a case where high speed silver halide grains are incorporated at a high silver coverage in a photosensitive material, however, it becomes impossible to disregard the effect of natural radiant rays, and so the products suffer a marked deterioration in photographic properties, including fog and granularity, upon storage.
As a means to solve such a problem, the art of designing a photosensitive material to have a reduced coverage of silver halides as a constituent thereof while ensuring a high photographic speed therein is disclosed in U.S. Pat. No. 5,091,293.
The aim of the art disclosed therein is to improve the drawbacks involved in reduction of silver coverage, e.g., decrease in photographic speed and deterioration in granularity, by the use of a core/shell emulsion having a high iodide content on the inside, the use of two-equivalent couplers, and the use of particular DIR compounds or silver halide grains having an aspect ratio of at least 5. However, such an art is insufficient to compensate for the lowering of sensitivity and the deterioration in granularity caused by a reduction of silver coverage. Therefore, it has been desired to further develop the arts of achieving an ultrahigh-speed of at least ISO 1000 while retaining excellent image quality.
On the other hand, it is also an urgent problem to further simplify and speed up photographic processing steps, because the weak point of silver halide photosensitive materials consists in the need to undergo photographic processing. A strong point of digital still cameras lies in requiring no liquid development steps. By contrast, the photographic processing of silver halide photographic materials requires exclusive processing equipment and careful management, and so can be performed at limited bases alone. A first reason therefor is that accurate control of compositions and temperatures is necessary for the processing baths to effect color development, bleaching and fixation, and technical information and skilled operations are required therefor. A second reason therefor is that, as the processing baths contain materials subject to ecological regulations against the discharge of their wastes, such as color developing agents and chelate compounds of iron as bleaching agents, exclusive facilities for installing developing apparatus therein are required in many cases. A third reason therefor is that, although the recent technological development has enabled a reduction in processing time, the photographic processing still costs time and is at a level insufficient to meet the demand for rapid reproduction of recorded images.
In view of these points, a number of improved arts have been proposed. For instance, IS & T's 48th Annual conference Proceedings, page 180, discloses the system wherein the bleach-fix bath, which is essential to conventional color photographic processing, is rendered unnecessary by transferring the dyes produced by development into a mordant layer and then peeling away the mordant layer. However, the art proposed therein still requires development with a processing bath containing a color developing agent, so that it cannot be said that such an art has resolved the environmental pollution problem.
With respect to the system which requires no processing solution containing a color developing agent, the pictrography system is proposed by Fuji Photo Film Co., Ltd. Although this system has an ecological advantage of being free of the aforesaid processing bath, it is a system for providing printed images by the transfer of diffusive dyes produced by development reaction into an image-receiving material. As far as it is unreformed, therefore, such a system is unsuitable for processing ultrahigh-speed picture-taking photosensitive materials as a subject of the present invention.